For separation and analysis of DNA, RNA and proteins using a microfluidic device, it is necessary to fill the fine channel thereof with a separation medium for changing the mobility according to the size of the molecule. Water soluble polymer solution is commonly used as a separation medium based on ease of filling into the channel and ease of replacement. Furthermore, it is common to perform optimization of the molecular weight (degree of polymerization) and concentration of the water soluble polymer solution according to the molecular weight of the sample to be analyzed. For example, if the sample is DNA of short chain length (hereinafter referred to as size), the molecular weight of the water soluble polymer solution would be reduced and its concentration increased, and if the sample is DNA of long chain length, the molecular weight of the water soluble polymer solution would be increased and its concentration reduced.
In this way, since the optimal conditions of the separation medium differ depending on the molecular weight of the sample to be analyzed, it has been necessary to prepare multiple types of water soluble polymers according to the application, and to have the user correctly select the water soluble polymer appropriate for the sample to be analyzed. For example, in the case of dsDNA fragment analysis, in order to achieve separation across a wide chain length range (also called size range) of 25 bp to 12000 bp, it was necessary to prepare at least three types of water soluble polymers. With just one type of water soluble polymer, the size range across which a high resolution can be obtained is limited, so it was difficult to achieve separation of samples of different size ranges at a high precision with a single type of water soluble polymer.